Method of producing decorative incandescent lamps



May 6, 1969 T- J. SENTEMENTES ETAL' METHOD OF PRODUCING DECORATIVE INCANDESCENT LAMPS Fild Dec. 30, 1966 FIG.3

FIG.4

COAT PATTERN CURE REMOVE DISPOSE ELASTOMERIC ELASTOMERIC ELASTOM RIC ELASTOMERIC RESlN CASE CASE RESIN FROM OVER LAMP PATTERN ENVELOPE THOMAS J. SENTEMENTES CARL POMROY INVENTORS BYM ATTORNEY United States Patent 3,442,987 METHOD OF PRODUCING DECORATIVE INCANDESCENT LAMPS Thomas J. Sentementes, Wakefield, and Carl Pomroy, Beverly, Mass., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Dec. 30, 1966, Ser. No. 606,114 Int. Cl. B29c 13/04 U.S. Cl. 264--1 4 Claims ABSTRACT OF THE DISCLOSURE A lamp is fabricated wherein an elastomeric resin case having peripheral grooves formed thereabout is disposed upon the lamp envelope to diffuse the light and cause the filament to appear to be elongated throughout the length of the lamp. The process of fabricating the lamp includes the steps of coating a pattern having the shape of the lamp envelope with an elastomeric resin, curing the resin, and then removing the elastomeric case formed and placing over the lamp.

BACKGROUND OF THE INVENTION Field of the invention This invention pertains to incandescent lamps and their manufacture, such lamps being designed for decorative and aesthetic values and illumination. Flame shaped lamps are an example of this type. A more specific aspect of this invention is the visual elongation of the filament of an incandescent lamp by means of a light-diffusing cover over the envelope.

Description of the prior art The prior art described a method of producing a lamp, the incandescent filament of which was visually modified by wrapping and fastening light transmitting yarn about the lamp envelope with an adhesive. This process required very close control during winding to get uniform spacing of the yarn, which resulted in reduced manufacturing efficiency. Furthermore, at steep inclines on the lamp envelope surface, accurate winding became more difficult, to the extent that at the tip of flame shaped lamps, there was no winding whatsoever, which detracted from the decorative effect of the lamp by appearing to cut off the top of the filament. The light emanating from the clear glass at the tip of the lamp presented an unpleasant contrast to the diffuse light emanating from the body. In addition, the uncovered glass at the tip reduced the mechanical and thermal shock resistance of the overall construction.

SUMMARY OF THE INVENTION An object of this invention is to improve the decorative effect of incandescent lamps when operating by diffusing all the light emanating therefrom and elongating the visual appearance of the filament.

We have discovered that covering the envelope of an incandescent lamp with a light transmitting elastomeric, peripherally grooved case causes the incandescent filament to appear to be elongated from the base to the tip thereof, and improves the decorative effect. Moreover, the elastomeric case also improves the thermal and mechanical shock resistance of the lamp. We have also discovered that coating a peripherally grooved pattern of the lamp with an elastomeric resin, curing the resin coating, removing from the pattern the elastomeric case formed and placing it over the lamp, will modify the visual appearance of the filament, as stated. This invention simplifies the manufacturing process of such lamps by eliminating ice the slow and inefficient procedure of winding yarn around each lamp envelope.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is an elevational view partly in section of an incandescent lamp in accordance with this invention.

FIGURE 2 is an elevational view of a pattern used in forming an elastomeric case.

FIGURE 3 is an enlarged cross sectional view taken on line 3--3 of FIGURE 1.

FIGURE 4 is a flow sheet of the process of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT An incandescent lamp in accordance with this invention comprises, in FIGURE 1, a base 1, a glass envelope 2, a peripherally grooved light transmitting elastomeric case 3, and a filament 4 within the envelope. The elastomeric case is formed by dipping body 6 of pattern 5 in FIGURE 2 into a liquid elastomeric resin. When coated, pattern 5 and the adhering resin thereon is then removed from the liquid, dried and cured, converting the resin into an integral case 3, with sufiicient elasticity to be stretched and removed from pattern 5, and capable thereafter of returning to its original general shape. The elastomeric case 3 is then again stretched, disposed on the glass envelope 2 and released, resulting in a tight fit and diffusing substantially all the light emanating from the lamp, when operating.

Another method of forming the elastomeric case 3 includes spraying the liquid elastomeric resin onto pattern 5, with the subsequent steps of the process being substantially identical to those of the process above.

Still another method of forming the case 3 includes the use of a fluidized bed, wherein an elastomeric resin in powder form is supported on a grid which is porous to air but not to the powder. When a current of air is directed up through the grid, the particles of powder are raised several inches and maintained in such agitation that a homogeneous fluidized bed is formed. Pattern 5 is then heated to the melting point of the resin, or hotter, and dipped into the fluidized bed, which results in the powder melting and adhering to pattern 5, forming a uniform coating.

Other methods of forming the elastomeric case 3 on pattern 5 will be apparent to those skilled in the art from the above examples.

The coating as now formed on pattern 5 is relatively weak and does not necessarily have the physical properties for use in this invention. Its chemical structure must be converted, such as by curing, to result in the tough elastic properties desired. Curing, as herein used, includes the definition on page 376 of part 27 of the 1966 A.S.T.M. standards, as follows: Cureto change the properties of a plastic or resin by chemical reaction, which, for example, may be condensation, polymerization, or addition; usually by the action of either heat or catalyst, or both, and with or without pressure.

This invention is not limited to any one class of elastomeric resins or plastics, since silicones, urethanes, and floroplastics as defined in Method D883-65aT of part 27 of 1966 A.S.T.M. standards have been successfully used. An example of an applicable silicone resin is a dimethyl. siloxane polymer. Polyvinylidene fluoride, dissolved in dimethyl formamide is an example of a fioroplastic used successfully. The reaction product of tolylenediisocyanate with a hydroxyl terminated polyester made from ethylene glycol and adipic acid is an example of a urethane plastic emobdied in our invention.

In addition to the specification mentioned above for the resin and plastics, a further requirement is the capability of the cured material to withstand the lamp en velope temperature, normally about 150 to 500 F., without substantial impairment of its physical and optical properties.

After curing, a case 3 is removed from pattern by distending case 3 sufficiently to pull it off pattern 5 or by immersing in an organic solvent, such as toluene, which softens and swells case 3 sufficiently for easy removal.

Case 3 is then disposed completely over glass envelope 2 of the lamp by distending the dry case 3 sufliciently for insertion of envelope 2 and releasing to return to its original shape or by inserting envelope 2 into the softened and still swollen case 3, and reducing case 3 to its original size and shape by completely evaporating the organic solvent used for swelling, some of which solvent is still contained therein. The evaporation may be accomplished by heat, or other suitable means.

When an incandescent lamp embodying this invention is operating, case 3 dilfuses the light emanating from the lamp and the peripheral grooves cause the lamp filament which is normally disposed about the major axis of the lamp to appear elongated along the major axis. The degree of visual elongation of the filament is a function of the number of grooves per inch on case 3. About 40 to 60 grooves per inch does not normally yield complete filament elongation, whereas about 70 to 80 grooves per inch causes the filament to appear completely elongated, substantially, from the base to the tip of the lamp. The maximum number of grooves per inch on case 3 is generally limited to the number that can be formed, such as by machining, on pattern 5. Pattern 5 can be made of metal or plastic, but metal is preferable because more grooves can be accurately formed on the metal pattern.

The depth of grooves 6 in FIGURE 3 affects the dilfusing of the light and visual elongation of the filament. For example, a depth of .006" to .012 results in a broader and less elongated appearance of the filament than a depth of .012" to .018". The maximum depth of grooves 6 is limited, generally, by the thickness of case 3. When the ratio of the depth of grooves 6 to the thickness of case 3 approaches about 60 to 90%, the tear strength of case 3 istoo low to permit removal from pattern 5 and disposing over the lamp without damage to case 3.

The thickness of case 3 is generally about 0.015 to 0.040 inch and is determined, primarily, by the desired elasticity and strength. A thickness of less than about 0.015 inch results in case 3 being too weak for removal from pattern 5 and disposing over the lamp without damage and a thickness greater than about 0.040 inch makes it more difiicult to remove case 3 from pattern 5 intact.

This invention is applicable to incandescent lamps having a bulbar shape, termiating in a straight or twisted tip opposite the base, chimney lamps, made to resemble a kerosene lantern, or other types of incandescent lamps whose function is both decorative and illuminative.

In a specific example for a 40 watt decor lamp, pattern 5 is made of chrominum plated brass, having 88 V-shaped grooves per inch, 0.018 inch deep machined into the surface. The pattern is then dipped into a liquid dimethyl siloxane polymer withthe viscosity adjusted to yield a coating 0.0-30 inch thick, for about 5 seconds, removed and allowed to drain about 10 minutes. The pattern and adhering resin coating are next heated in an oven at 35 0 F. for minutes, whereby the resin is cured to yield elastomeric case 3. The pattern, with case 3 thereon, is removed from the oven and while still hot immersed completely in toluene for 3 minutes, whereby case 3 is softened and swollen, and is removed easily from the pattern. Immediately, while case 3 is still swollen, the lamp is inserted into the case and then heated by means of heat lamps, whereby the toluene still contained in case 3 is evaporated and case 3 shrinks back to its original size, resulting in a close fit of the elastomeric case on the lamp envelope.

The filament of said 40 watt lamp is mounted within the lamp envelope about midway between the base and the tip of the lamp. Lead-in wires support and electrically connect the two ends of the W-shaped filament and individual wires support the three vertices. At the middle vertex, the filament is bent so that the triangle formed by the points of the middle vertex and two ends of the filament is orthogonal too, and approximately centered about, the major axis of the lamp.

When the lamp, according to this invention, is operated the filament does not appear to be W-shaped and disposed about the axis of the lamp. Instead, the grooves on the elastomeric case diffuse the light emanating from the lamp in such a manner that the filament appears to be elongated from the base to the tip of the lamp, producing a softer, more decorative efiect than that from a lamp whose filament does not appear elongated.

As our invention we claim:

1. In the method of Covering an incandescent lamp envelope wherein an elastomeric case is disposed about the envelope, the improvement which comprises:

forming a coating of an elastomeric resin on a pattern having the general shape of an incandescent lamp envelope;

said pattern having peripheral grooves disposed thereabout, said grooves being substantially disposed about the entire surface of said pattern;

curing said coating to form a light transmitting elastomeric case;

removing said elastomeric case from said pattern, and

disposing said elastomeric case about said lamp en velope, whereby substantially all the light emanating from said lamp passes through, and is difi'used by, said case, causing the visual appearance of the filament of said lamp to be elongated.

2. The process according to claim 1, wherein said resin is one of the group consisting of silicone, urethane, and fioroplastics.

3. The process according to claim 1, wherein the peripheral grooves on said pattern are 0.004 to 0.024 inch deep at a pitch of 40 to grooves per inch.

4. The process according to claim 3, wherein said lamp envelope has a bulbar shape, tapering into a tip at the end opposite the base.

References Cited UNITED STATES PATENTS 2,183,691 12/1939 Owens.

3,002,231 10/1961 Walkter et al 264-301 X 3,009,209 11/ 1961 Weinbrenner et al. 264-3 09 X 3,116,885 1/1964 Morse 240-92 3,148,235 9/1964 Velonies et al. 264-301 1,937,537 12/1933 Walthor 313-318 2,683,767 7/1954 Cunningham 220-21 3,127,295 3/1964 Thorington 220-2.1 3,223,273 12/ 1965 Thorington 2202.1

OTHER REFERENCES Checkel, R. L: Modern Plastics, October 1958, pp. l32.

ROBERT F. WHITE, Primary Examiner.

K. J. HOVET, Assistant Examiner.

US. Cl. X.R. 

